Technical Field
[0001] The present invention relates to a headphone device and specifically, a headphone
device including a speaker array which has a plurality of speaker units.
Background Art
[0002] Conventional studies have been carried out related to sound field reproduction method.
Regarding speaker reproduction, surround reproduction such as 5.1 ch. and 7.1 ch.
is generally proposed and is commercialized. An advantage of this technique is to
use speakers called rear surround sound speakers, as well as front speakers and in
combination they are capable of reproducing rear and environmental sounds.
[0003] However, a problem arises during the surround sound reproduction to find the best
ideal sound field point for listening in a service area of the installation center,
of which is limited. In addition, in surround sound reproduction, there is a problem
that it is difficult to arrange the speakers in a rear position in an actual home.
[0004] As a measure to solve the problem concerning the speaker arrangement, there is a
front surround speaker using a transoral technique. In the front surround speaker,
virtual surround sound can be enjoyed by using only the front speaker and using a
head-related transfer function. The advantage of the technique is that the speaker
can be easily installed and the system is simple. On the other hand, there is a problem
that individual variations in the effect may occur because the head-related transfer
function is used. In addition, also in the technique, there is a problem concerning
the listening position that the ideal position for the reproduction is limited.
[0005] As a measure to solve the problem concerning the listening position, there is a sound
field reproduction technique using wave field synthesis (see, NPL 1). This is such
a technique that the sound field inside a closed curved surface can be completely
controlled if a speaker array is configured, and a sound pressure having the closed
curved surface shape which does not include a sound source and a particle velocity
in the normal direction can be completely controlled. When using the sound field reproduction
technique which uses wave field synthesis, the sound field inside the closed curved
surface is completely reproduced and the degree of freedom of the listening position
is also increased.
[0006] For example, in PTL 1, a three-dimensional sound field reproduction device is disclosed
in which a plurality of speakers of the speaker array cover the entire head of the
listener and a high level of realism can be reproduced. However, in the three-dimensional
sound field reproduction device, since the plurality of speakers are used and to configure
the array is needed, there is a problem that the scale becomes large. In addition,
in a case of using the speaker array, there is a problem in that the frequency band
to be reproduced is limited by the distance between the speakers due to a problem
of spatial aliasing.
[0007] On the other hand, in the field of headphone reproduction, there is a virtual surround
sound using the head-related transfer function. When using the virtual surround, it
is possible to ideally enjoy sound field with a handy headphone device and the problem
concerning the listening position does not occur.
Citation List
Patent Literature
[0008] PTL 1: Japanese Unexamined Patent Application Publication No.
2008-118559
Non Patent Literature
[0009] NPL 1: "
Study on Three-Dimensional Virtual Reality based on Kirchhoff's Integral Equation",
Waseda University, Advance Research Institute for Science and Engineering, Acoustic
Laboratory, Yoshio YAMAZAKI, [online], April, 1997, (search October 1, 2010], Internet
<URL: http:www.acoust.rise.waseda.ac.jp/publications/happyou/1997-h9.html>
Summary of Invention
Technical Problem
[0011] However, as described above, in virtual surround sound using the head-related transfer
function in the field of the headphone reproduction, since the sound pressure in the
vicinity of an entrance of the external auditory meatus is duplicated as "a point",
there is a problem that influence of the individual auricle cannot be considered and
an ideal effect cannot be obtained depending on an individual. In addition, generally,
since the headphone has a shape blocking the ear, there is a problem that external
sound cannot be heard even though a feeling of being out of the head may be obtained
with virtual surround sound.
[0012] An object of the present invention is to provide a headphone device in which the
influence of individual differences in virtual sound field reproduction is less likely
to occur and which is capable of listening to the external sound naturally.
Solution to Problem
[0013] The concept of the present invention is a headphone device including:
a left and a right speaker array each formed of a plurality of speaker units arranged
in a single circle instead of a double circle or a triple circle, arranged in use
to surround and not block the auricle of the listener,
wherein each speaker array reproduces, using a wave field synthesis, a sound field
inside a closed curved surface having a sound pressure and particle velocity at a
number of points on the closed curved surface, the closed curved surface being in
the vicinity of the auricle in use.
[0014] In the present invention, the speaker array is included. The speaker array formed
of the plurality of speaker units arranged to surround the auricle. Then, the sound
field inside the closed curved surface in the vicinity of the auricle is reproduced
by the speaker array using the wave field synthesis. In this case, a sound pressure
signal as a driving signal for causing the sound emitted at each position of speaker
units is supplied to the plurality of speaker units of the speaker array so as to
reproduce the sound field inside the closed curved surface in the vicinity of the
auricle.
[0015] As described above, in the present invention, the sound field inside the closed curved
surface in the vicinity of the auricle is reproduced by the speaker array using the
wave field synthesis, and since reverberation or a diffraction effect occurs in the
ear of an individual, the influence caused by individual differences is less likely
to occur. In addition, in the present invention, the speaker array is formed of the
plurality of the speaker units arranged to surround the auricle and is not of a shape
that blocks the ear of the listener, and then the external sound can be heard naturally.
[0016] In the present invention, for example, the plurality of speaker units of the speaker
array may be arranged to be inclined inwardly towards the closed curved surface. Accordingly,
a propagation velocity of the particles in all up and down, and left and right directions
can be reproduced satisfactorily inside the closed curved surface. For example, the
headphone device may further include a donut-shaped ear pad having an opening portion
in which the auricle may be inserted, and the plurality of speaker units of the speaker
array may be arranged along a circular end portion which is opposite to an abutting
side of a listener of the ear pad.
[0017] Further, in the present invention, for example, a distance Δd [m] of the plurality
of the speaker units of the speaker array may satisfy a formula of Δd < c/(2·fmax),
when a reproduction maximum frequency is fmax [Hz] and a sound velocity is c [m/s].
Accordingly, a frequency band up to the reproduction maximum frequency fmax [Hz] can
be reproduced.
Advantageous Effects of Invention
[0018] According to the present invention, the influence of individual differences in the
virtual sound field reproduction is less likely to occur and the external sound may
be heard naturally. In other words, since the sound field inside the closed curved
surface in the vicinity of the auricle is reproduced by the speaker array using the
wave field synthesis, and reverberation or a diffraction effect occurs in the ear
of an individual, the influence caused by individual differences is less likely to
occur. In addition, the speaker array has the plurality of the speaker units arranged
to surround the auricle and is not of a shape that blocks the ear of the listener,
and then the external sound can be heard naturally.
Brief Description of Drawings
[0019]
[Fig. 1] Fig. 1 is a view illustrating a configuration example of a headphone device
as an embodiment of the present invention.
[Fig. 2] Fig. 2 is a view illustrating an example of a closed curved surface in which
a sound field is reproduced by a speaker array included in a headphone body.
[Fig. 3] Fig. 3 is a view for explaining that a plurality of speaker units of the
speaker array included in the headphone body arranged to be inclined inwardly towards
the closed curved surface in which the sound field is reproduced.
[Fig. 4] Fig. 4 is a view for explaining that the plurality of the speaker units of
the speaker array are arranged along a circular end portion of an ear pad which is
opposite to an abutting side of a listener.
[Fig. 5] Fig. 5 is a view for explaining an arrangement distance of the plurality
of the speaker units of the speaker array included in the headphone body.
[Fig. 6] Fig. 6 is a block diagram illustrating a configuration example of a circuit
which supplies a sound pressure signal to each speaker unit of the speaker array included
in the headphone body.
Description of Embodiments
[0020] Hereinafter, a mode (referred to as "an embodiment" below) for carrying out the present
invention will be described. In addition, the description will be made in the following
order.
- 1. Embodiment
- 2. Modification Example
<1. Embodiment>
[Configuration Example of Headphone Device]
[0021] Figs. 1(a) to (c) illustrate a configuration example of a headphone device 100 as
the embodiment. Fig. 1(a) is a top view, Fig. 1(b) is a front view and Fig. 1(c) is
a side view thereof. The headphone device 100 is configured such that a left-side
headphone body 120L and a right-side headphone body 120R are connected to front end
portions of the left and right of a head band 110, respectively.
[0022] The left-side headphone body 120L has a speaker array 130. The speaker array 130
is formed of a plurality of speaker units 131 which are arranged to surround the auricle
(left-side) of a listener. The speaker array 130 included in the left-side headphone
body 120L reproduces a sound field inside a closed curved surface 140L in the vicinity
of the auricle (left-side) illustrated in Fig. 1(b) using a wave field synthesis.
A sound pressure signal as a driving signal for causing the sound to be emitted at
each position of speaker units 131 is supplied to a plurality of speaker units 131
of the speaker array 130 included in the left-side headphone body 120L so that the
sound field inside the closed curved surface 140L can be reproduced.
[0023] The right-side headphone body 120R also has the speaker array 130. The speaker array
130 is formed of a plurality of the speaker units 131 which are arranged to surround
the auricle (right-side) of a listener. The speaker array 130 included in the right-side
headphone body 120R reproduces a sound field inside a closed curved surface 140R in
the vicinity of the auricle (right-side) illustrated in Fig. 1(b) using the wave field
synthesis. The sound pressure signal as the driving signal for causing the sound to
be emitted at each position of speaker units 131 is supplied to a plurality of speaker
units 131 of the speaker array 130 included in the right-side headphone body 120R
so that the sound field inside the closed curved surface 140R can be reproduced.
[0024] In addition, with respect to the wave field synthesis, a detailed description thereof
will be omitted, however, for example, there is a method or the like in which the
Kirchhoff's integral formula is used as indicated in the "Study on Three-Dimensional
Virtual Reality based on Kirchhoff's Integral Equation", Yoshio YAMAZAKI. In the method,
the sound field inside a closed curved surface S is reproduced by discretizing the
closed curved surface S at N points and by reproducing a sound pressure P (rj) and
a particle velocity un (rj) at the N points on the closed curved surface S. In the
embodiment, the sound pressure signal supplied to each of the speaker units 131 of
the speaker array 130 included in the headphone bodies 120L and 120R is generated,
based on the wave field synthesis described above.
[0025] Fig. 2(a) illustrates an example of the closed curved surface 140L in which the sound
field is reproduced by the speaker array 130 included in the left-side headphone body
120L. The closed curved surface 140L is a narrow region having a diameter of 8 to
10 cm around the external auditory meatus when viewed from the side head portion of
the human (the listener). Fig. 2(b) illustrates a positional relationship between
the left-side headphone body 120L and the closed curved surface 140L in a case where
the headphone 100 is mounted. In addition, even though detailed description is omitted,
similarly, the closed curved surface 140R in which the sound field is reproduced by
the speaker array 130 included in the right-side headphone body 120R is a narrow region
having a diameter of 8 to 10 cm around the external auditory meatus.
[0026] As illustrated in Fig. 3, the plurality of speaker units 131 of the speaker array
130 included in the headphone bodies 120L and 120R are arranged to be inclined inwardly
towards the closed curved surfaces 140L and 140R in which the sound field is reproduced.
In other words, a central axis S of each speaker unit 131 is inclined towards a central
axis Z of the speaker array 130. As described above, since the plurality of the speaker
units 131 of the speaker array 130 are arranged to be inclined, a propagation velocity
of the particles in all directions of up and down, and left and right can be reproduced
satisfactorily inside the closed curved surfaces 140L and 140R.
[0027] In Fig. 1 described above, even though the illustration is omitted, the headphone
bodies 120L and 120R include donut-shaped ear pads 150 having opening portions in
which the auricle can be inserted, respectively. As illustrated in Fig. 4, the plurality
of the speaker units 131 of the speaker array 130 described above are arranged along
a circular end portion 150a of the ear pad 150, which is opposite to an abutting side
of the listener.
[0028] As illustrated in Fig. 5, the plurality of the speaker units 131 of the speaker array
130 included in the headphone bodies 120L and 120R are arranged having a distance
Δd [m]. The distance Δd [m] satisfies the following formula (1), when a reproduction
maximum frequency is fmax [Hz]. In this regard, c is a sound velocity (approximately,
340 m/s). Accordingly, a frequency band up to the reproduction maximum frequency fmax
[Hz] can be reproduced.
![](https://data.epo.org/publication-server/image?imagePath=2016/16/DOC/EPNWB1/EP11834286NWB1/imgb0001)
[0029] In general, the wave field synthesis system has a problem of spatial aliasing. The
aliasing occurs at a frequency of a value that divides the sound velocity by twice
of the distance and a reproducible boundary frequency is determined, based on the
concept of spatial sampling. For example, when the speaker units are arranged in a
distance of 5 cm, appropriately 3.4 kHz is the frequency of the spatial aliasing.
This is an extremely low frequency compared to 20 kHz that is an audible band of a
human. The spatial aliasing frequency falias [Hz] is indicated as the following formula
(2).
![](https://data.epo.org/publication-server/image?imagePath=2016/16/DOC/EPNWB1/EP11834286NWB1/imgb0002)
[0030] The upper limit of the frequency rises when narrowing the distance thereof, which
means that the sound pressure emitted from the speaker unit 131 is reduced. In addition,
there is a trade-off relationship between the spatial aliasing and the sound pressure,
and the sound field is difficult to reproduce in a large room. However, in the headphone
device 100, since the speaker array 130 is in the vicinity of the auricle, a sufficient
sound pressure can be presented to the listener even though the speaker unit 131 is
small. For example, when using a super small-sized speaker unit of 8 mm, since Δd=0.008
m, the spatial aliasing frequency falias is 20 kHz or more and a sufficient sound
field can be reproduced, by the formula (2).
[0031] Fig. 6 illustrates a configuration example of a circuit of the headphone body 120
(120L and 120R). The sound pressure signal corresponding to each of the speaker units
131 of the speaker array 130 is supplied from a sound pressure signal output portion
160 to the headphone body 120. As described above, the sound pressure signal is generated,
based on wave field synthesis. For example, the sound pressure signal can be obtained
by collecting the sound with a microphone which is arranged at a position of each
of the speaker units. In addition, for example, the sound pressure signal can be obtained
by carrying out a conversion process in a multi-channel signal such as 5.1 ch. and
7.1 ch.
[0032] The headphone body 120 has a digital filter portion 121, a D/A converter 122 and
an amplifier circuit 123 as well as the speaker array 130. The sound pressure signal
corresponding to each of speaker units 131 from the sound pressure signal output portion
160 is supplied to the speaker array 130 via the D/A converter 122 and the amplifier
circuit 123 after the filter process is performed in the digital filter portion 121.
[0033] For example, the filter process in the digital filter portion 121 is a filter process
for the control of the region. In this case, the sound emitted from each of the speaker
units 131 of the speaker array 130 is the sound in a position slightly more inside
than the position of the speaker unit 131 and is less likely to receive the influence
of the spatial aliasing. In addition, for example, the filter process in the digital
filter portion 121 is a filter process for correcting characteristics of each of the
speaker units 131.
[0034] As described above, in the headphone device 100 illustrated in Fig. 1, the sound
field inside the closed curved surfaces 140L and 140R in the vicinity of the auricle
is reproduced by the speaker array 130 included in the headphone bodies 120L and 120R
using the wave field synthesis. Accordingly, since reverberation or a diffraction
effect occurs in the ear of an individual, the influence caused by individual differences
is less likely to occur in the virtual sound field reproduction. In other words, the
individual differences can be eliminated with a simple system of the headphone type
compared to the speaker reproduction.
[0035] In addition, in the headphone device 100 illustrated in Fig. 1, the speaker array
130 included in the headphone bodies 120L and 120R has the plurality of the speaker
units 131 which are arranged to surround the auricle. Accordingly, the speaker array
130 is not of a shape that blocks the ear of the listener and the external sound can
be heard naturally. Accordingly, an effect combining the virtual sound field and the
sound field of the real world, which is not possible in the headphone device of the
related art, can also be present and natural conversation between two persons is also
possible while the headphone device is worn.
<2. Modification Example>
[0036] In addition, the above embodiment is illustrated in such a manner that the plurality
of the speaker units 131 are arranged in a circle in the speaker array 130 included
in the headphone bodies 120L and 120R. However, the plurality of speaker units 131
may not be arranged in a circle and it may be arranged in an ellipse, in a square
or in other shapes. In a word, speaker units may be arranged to surround the auricle.
In addition, the above embodiment is illustrated in such a manner that the plurality
of the speaker units 131 are arranged in a single circle in the speaker array 130
included in the headphone bodies 120L and 120R, however, in an example not forming
part of the invention, a configuration which is arranged in double circles or triple
circles may be considered.
Reference Signs List
[0037]
- 100
- headphone device
- 110
- head band
- 120
- headphone body
- 120L
- left-side headphone body
- 120R
- right-side headphone body
- 121
- digital filter portion
- 122
- D/A converter
- 123
- amplifier circuit
- 130
- speaker array
- 131
- speaker unit
- 140L, 140R
- closed curved surface
- 150
- ear pad
- 150a
- circular end portion
- 160
- sound pressure signal output portion
1. A headphone device (100) comprising:
a left speaker array (130) and a right speaker array (130) each formed of a plurality
of speaker units (131) arranged in a single circle instead of a double circle or a
triple circle, arranged in use to surround and not block an auricle of a listener,
wherein each speaker array reproduces, using a wave field synthesis, a sound field
inside a closed curved surface (140) having a sound pressure and particle velocity
at a number of points on the closed curved surface, the closed curved surface being
in the vicinity of the auricle in use.
2. The headphone device according to claim 1,
wherein the plurality of speaker units of the speaker array are arranged to be inclined
inwardly towards the closed curved surface.
3. The headphone device according to claim 2, further comprising:
a donut-shaped ear pad (150) having an opening portion in which the auricle is able
to be inserted, and
wherein the plurality of speaker units of the speaker array are arranged along a circular
end portion which is opposite to an abutting side of a listener of the ear pad.
4. The headphone device according to claim 1,
wherein a distance Δd [m] of the plurality of speaker units of the speaker array satisfies
the following formula, when a reproduction maximum frequency is fmax [Hz] and a sound
velocity is c [m/s],
5. The headphone device according to claim 1,
wherein the plurality of the speaker units of the speaker array are inclined inwardly
towards the closed curved surface such that a propagation velocity of particles in
all directions of up and down, and left and right is able to be reproduced inside
the closed curved surface.
6. The headphone device according to claim 1,
wherein the closed curved surface is a region having a diameter of 8 to 10 cm around
the external auditory meatus when viewed from a side head portion.
7. The headphone device according to claim 1, comprising:
a digital filter portion (121) which carries out a filter process on a sound pressure
signal corresponding to each of the speaker units, for controlling a region and for
correcting characteristics of the speaker units.
1. Kopfhörervorrichtung (100), die Folgendes umfasst:
eine linke Lautsprecheranordnung (130) und eine rechte Lautsprecheranordnung (130),
die jeweils aus mehreren Lautsprechereinheiten (131), die in einem einzelnen Kreis
anstelle eines zweifachen Kreises oder eines dreifachen Kreises angeordnet sind, gebildet
sind, und die im Gebrauch angeordnet sind, eine Ohrmuschel eines Zuhörers zu umgeben
und nicht zu blockieren,
wobei jede Lautsprecheranordnung unter Verwendung einer Wellenfeldsynthese ein Schallfeld
innerhalb einer geschlossenen, gekrümmten Oberfläche (140) wiedergibt, das einen Schalldruck
und eine Teilchengeschwindigkeit an mehreren Punkten auf der geschlossenen, gekrümmten
Oberfläche besitzt, wobei sich die geschlossene, gekrümmte Oberfläche im Gebrauch
in der Nähe der Ohrmuschel befindet.
2. Kopfhörervorrichtung nach Anspruch 1,
wobei die mehreren Lautsprechereinheiten der Lautsprecheranordnung so angeordnet sind,
dass sie einwärts in Richtung der geschlossenen, gekrümmten Oberfläche geneigt sind.
3. Kopfhörervorrichtung nach Anspruch 2, die ferner Folgendes umfasst:
ein torusförmiges Ohrpolster (150), das einen Öffnungsabschnitt besitzt, in den die
Ohrmuschel eingeführt werden kann, und
wobei die mehreren Lautsprechereinheiten der Lautsprecheranordnung entlang eines kreisförmigen
Endabschnitts, der sich gegenüber einer an einen Zuhörer angrenzenden Seite des Ohrpolsters
befindet, angeordnet sind.
4. Kopfhörervorrichtung nach Anspruch 1,
wobei ein Abstand Δd [m] der mehreren Lautsprechereinheiten der Lautsprecheranordnung
die folgende Formel erfüllt, wenn die maximale Wiedergabefrequenz fmax [Hz] ist und
die Schallgeschwindigkeit c [m/s] ist:
5. Kopfhörervorrichtung nach Anspruch 1,
wobei die mehreren Lautsprechereinheiten der Lautsprecheranordnung so einwärts in
Richtung der geschlossenen, gekrümmten Oberfläche geneigt sind, dass eine Ausbreitungsgeschwindigkeit
von Teilchen in alle Richtungen, nach oben und unten und nach links und rechts, innerhalb
der geschlossenen, gekrümmten Oberfläche reproduziert werden kann.
6. Kopfhörervorrichtung nach Anspruch 1,
wobei die geschlossene, gekrümmte Oberfläche eine Region ist, die einen Durchmesser
von 8 bis 10 cm um den äußeren Gehörgang herum besitzt, wenn sie von einem seitlichen
Kopfabschnitt aus betrachtet wird.
7. Kopfhörervorrichtung nach Anspruch 1, die Folgendes umfasst:
einen digitalen Filterabschnitt (121), der einen Filterprozess an einem Schalldrucksignal,
das jeder Lautsprechereinheit entspricht, ausführt, um eine Region zu kontrollieren
und um Eigenschaften der Lautsprechereinheiten zu korrigieren.
1. Dispositif casque d'écoute (100) comprenant :
un réseau de haut-parleurs gauche (130) et un réseau de haut-parleurs droit (130)
constitués chacun d'une pluralité d'unités haut-parleur (131) agencées suivant un
seul cercle plutôt qu'un cercle double ou un cercle triple, agencés en service de
manière à entourer et non bloquer un pavillon auriculaire d'un auditeur,
dans lequel chaque réseau de haut-parleurs reproduit, au moyen d'une synthèse de champ
d'onde, un champ sonore à l'intérieur d'une surface courbe fermée (140) présentant,
en un certain nombre de points, une certaine pression sonore et vitesse de particules,
la surface courbe fermée se situant en service au voisinage du pavillon auriculaire.
2. Dispositif casque d'écoute selon la revendication 1,
dans lequel la pluralité d'unités haut-parleur du réseau de haut-parleurs sont agencées
de manière à s'incliner vers l'intérieur en direction de la surface courbe fermée.
3. Dispositif casque d'écoute selon la revendication 2, comprenant en outre :
un coussinet d'oreille torique (150) doté d'une partie formant ouverture dans laquelle
le pavillon auriculaire est susceptible de s'introduire, et
dans lequel la pluralité d'unités haut-parleur du réseau de haut-parleurs sont agencées
suivant une partie extrémité circulaire opposée à un côté en butée d'un auditeur du
coussinet d'oreille.
4. Dispositif casque d'écoute selon la revendication 1,
dans lequel une distance Δd [m] de la pluralité d'unités haut-parleur du réseau de
haut-parleurs vérifie la formule suivante, dans laquelle fmax [Hz] représente une
fréquence de reproduction maximale et c [m/s] la vitesse du son,
5. Dispositif casque d'écoute selon la revendication 1,
dans lequel la pluralité d'unités haut-parleur du réseau de haut-parleurs s'inclinent
vers l'intérieur en direction de la surface courbe fermée de sorte à permettre la
reproduction, à l'intérieur de la surface courbe fermée, d'une vitesse de propagation
de particules dans toutes les directions à savoir vers le haut et le bas et vers la
gauche et la droite.
6. Dispositif casque d'écoute selon la revendication 1,
dans lequel la surface courbe fermée est une région présentant un diamètre de 8 à
10 cm autour du conduit auditif externe, vue d'une partie de côté de la tête.
7. Dispositif casque d'écoute selon la revendication 1, comprenant :
une partie formant filtre numérique (121) qui soumet à un processus de filtrage un
signal de pression sonore correspondant à chacune des unités haut-parleur aux fins
de réguler une région et aux fins de corriger des caractéristiques des unités haut-parleur.